The possibility that a variety of psychoactive drugs exert certain of their effects by acting as novel or distracting stimuli is being examined in experiments which compare drug effects with effects of nondrug stimuli and in studies in which the effects of removing drugs after chronic administration are being studied. The behavioral effects of interest are the disruption of control by discriminative stimuli visual discriminative stimuli in visual discrimination experiments and the rate-dependent alterations of responding on fixed interval reinforcement schedules. Rats and pigeons are being used, and drugs being administered include scopolamine, d-amphetamine, anf LSD. BIBLIOGRAPHIC REFERENCES: Ksir, C. Sopolamine and amphetamine effects on discrimination: Interaction with stimulus control. Psychopharmacologia (Berl.) 43, 37-41, 1975. (b) in press: Ksir, C. Rate-dependent drug effects: Possible state dependency. Pharmacology Biochemistry and Behavior, February, 1976.